Additive for oil-based lubricants having improved extreme pressure properties

ABSTRACT

The present invention relates to a novel additive for oil-based lubricants having improved extreme-pressure properties, to a method for producing said novel additive, to oil-based lubricants containing said novel additive and to uses of said novel additive.

The present invention relates to a novel additive for oil-basedlubricants having improved extreme pressure properties, to a process forproducing this novel additive, to oil-based lubricants comprising thisnovel additive and to uses of this novel additive.

The phenomena of friction, lubrication and wear are of enormouspractical significance. Attempts are made to reduce the major losses ofmaterial and energy which are caused by wear by careful materialselection, surface coating, surface hardening and lubrication. One ofthe most important demands on a lubricant is for it to give effectivesurface protection of the materials. Various friction phenomena occur inunlubricated metal surfaces which move against one another under stress.In many cases, abrasive wear extending as far as microscale wear of theworkpieces is observed. The use of lubricants serves to distinctlyreduce material wear by abrasion, which accompanies dry friction.

The finding that pure base oils, whether they are mineral oils orsynthetic oils, cannot assure effective protection of highlymechanically stressed surfaces led to the addition of additives as earlyas the turn of the last century. It is only these additives that helpthe lubricant oil to attain the desired use properties. The aim is thusto enhance positive properties and to eliminate or minimize unwantedproperties. The amount of additives mixed in varies according to theapplication from a few ppm up to concentrations of 20%.

As well as the control of the physical properties of a lubricant oil,for instance the viscosity as a hydrodynamic parameter, it is possibleto chemically modify the lubricant and surface. One of the mostimportant demands on a lubricant additive is the surface protection ofthe materials, which prevents or at least greatly reduces abrasive wearand microscale wear between metal surfaces. This property is assured bywhat are called antiwear (AW) and extreme pressure (EP) activeingredients.

Frequently, especially in steelworking, mid-chain chloroparaffins(C14-C17) are still being used as extreme pressure (EP) additives inspite of considerable concerns with regard to the environment andhealth. Because of these negative properties of chloroparaffins, thereis a considerable need for substitutes that are not of ecological andtoxicological concern for the various fields of use. In the lubricantssector, however, it has not been possible to entirely displacechloroparaffins from many applications, since they have excellentperformance, especially at extreme pressures. The main field of use forchloroparaffins is forming technology (deep drawing, thread forming,etc.).

Owing to environmental relevance, chloroparaffins have partly beenreplaced by more ecologically acceptable zinc compounds, for example byzinc dialkyldithiophosphates, zinc complexes of alkyl dithiophosphates(RO)2P(S)SH having the general empirical formula Zn[(RO)2PS2]2. Thesecompounds are among the layer-forming active ingredients, although thecomponents that are actually active are not the complexes themselves butthe reaction or breakdown products which arise in frictional processesunder stress. Regrettably, these zinc compounds by no means offer the EPperformance of the chloroparaffins.

Further known lubricant additives are thiadiazoles, which are known asadditives having good separating action and high pressure absorptioncapacity (EP) and additionally offer very good corrosion protection,especially in the case of nonferrous metals. The monomericthiadiazoles—also referred to as dimercaptothiadiazole—are thereforeused mainly as nonferrous metal deactivators, as described inEP2228425A1, and are sold, for example, under the “Additin RC8210” or“Additin RC 5201” names by RheinChemie Rheinau GmbH. The monomericthiadiazoles are generally colorless clear liquids which are soluble inoily hydrophobic media. However, the EP properties in the case ofmonomeric thiadiazole are still inferior to those of the abovementionedzinc compounds, such as zinc dithiophosphate or zinc dithiocarbamate.

Dimeric 2,5-dimercapto-1,3,4-thiadiazole is commercially available underthe “Vanlube 829” name from the Vanderbilt Company, USA, and unlike themonomers has very good EP properties. It is a compound which finds usemainly in greases or pastes, but not in liquid oily (hydrophobic) media.The reason for the very restricted use is that the pulverulent substanceis insoluble in hydrophobic systems and cannot be dispersed effectivelybecause of the relatively high density (2.09 g/cm³). However, a maximumfineness of distribution of 2,5-dimercapto-1,3,4-thiadiazole in thematrix is a prerequisite for effective performance.

In summary, it can thus be stated that the lubricant additives knownfrom the prior art are either of ecological or toxicological concern,have inadequate EP performance or cannot be used viably in liquid oily(hydrophobic) media.

It is thus an object of the present invention to develop a lubricantsystem which avoids the abovementioned disadvantages of the prior art.

This object is achieved in accordance with the invention by a processfor producing a lubricant additive, which is characterized in that

a)

-   -   i) a dimeric thiadiazole compound, especially a        bis(2-alkyl-1,3,4-thiadiazolyl) 5,5′-disulfide derivative of the        formula (I)

-   -   -   and/or a dimeric 2,5-dimercapto-1,3,4-thiadiazolethiol            derivative of the formula (II)

-   -   -   where n in the formulae (I) and (II) is 1 or 2 and        -   R1 and R2 are each independently hydrogen, linear or            branched alkyl groups having 1 to 12 carbon atoms,            especially thioalkyl groups (—SR) having 1 to 12 carbon            atoms, aromatic radicals or heteroaromatic radicals,

    -   ii) is dissolved in a polyamine or polyamine derivative of the        formula (III)

R1-(CH2-CH2-NH)n-CH2-CH2-R2  (III)

-   -   -   where n in formula (III) is an integer from 1 to 15,            especially an integer from 3 to 8, and R1 and R2 are each            independently hydrogen, —NH2, linear or branched alkyl            groups having 1 to 12 carbon atoms or a modified or            unmodified succinimide group, and

    -   iii) a compound of the formula (IV)

-   -   -   in which n is an integer from 1 to 8, especially an integer            from 3 to 8, preferably 6, is added to the solution            obtained,

    -   or        b)

    -   i) a dimeric thiadiazole compound, especially a        bis(2-alkyl-1,3,4-thiadiazolyl) 5,5′-disulfide derivative of the        formula (I)

-   -   -   and/or a dimeric 2,5-dimercapto-1,3,4-thiadiazolethiol            derivative of the formula (II)

-   -   -   where n in the formulae (I) and (II) is 1 or 2 and        -   R1 and R2 are each independently hydrogen, linear or            branched alkyl groups having 1 to 12 carbon atoms,            especially thioalkyl groups (—SR) having 1 to 12 carbon            atoms, aromatic radicals or heteroaromatic radicals,

    -   ii) is dissolved in a polyol, especially a polyether polyol        having a high propylene oxide content, i.e. having a low ethyl        oxide/propylene oxide ratio, and/or a triglyceride having a        hydroxy fatty acid component, and

    -   iii) a hydrophobic phenol derivative and/or unsaturated fatty        alcohol is added to the solution obtained.

The component process steps a) ii) and a) iii), or b) ii) and b) iii),can be combined if desired to give one step in each case.

A dimeric thiadiazole compound usable with preference in a) i) or b) i)is 5,5′-dithiobis(1,3,5-thiadiazole-2-thiol) with R1 and R2=H (CAS no.:72676-55-2) which is shown in formula (IIa):

A dimeric thiadiazole compound likewise usable in accordance with theinvention is bis[2,5-dithio-1,3,4-thiadiazole] (formula VIII), which isdescribed, for example, in EP1702918 A2 to RHEIN-CHEMIE RHEINAU GmbH.

Also usable in accordance with the invention are compounds of theformulae (I) and (II) wherein the R radicals are alkyl or thioalkylgroups. With increasing chain length of the alkyl groups on R1 and R2,the solubility in hydrophobic media increases stepwise. These sidegroups make an ever greater contribution to reducing the friction valuewith growing chain length, but can have an adverse effect on the EPproperties. The load-bearing capacity tends to increase with the numberof sulfur atoms in the molecule, and the solubility in hydrophobic mediatends to decrease at the same time.

In order to combine high load-bearing capacity with simultaneously highlubricity (friction value reduction), it is possible for the personskilled in the art, according to the requirement, to combine differentdimeric thiadiazole compounds of the formulae (I) and (II) with oneanother as appropriate.

The compounds of the formulae (I) and (II) are used in accordance withthe invention in alternative a) with a proportion by weight of 4% to13%, preferably 8% to 10%.

Polyamines or polyamine derivatives of the formula (III) which arepreferred in accordance with the invention are those which, rather thanR1 or R2, independently contain a succinimide group. Particularpreference is given to the monosuccinimide derivative having CAS no.67762-72-5, which is shown in the formula (V),

in which R is a polyisobutylene radical having a molecular weight in therange of 500-2500. Particular preference is likewise given to thebissuccinimide derivative having CAS no. 84605-20-9, which is shown inthe formula (VI),

in which n is an integer from 1 to 8 and R a polyisobutylene radicalhaving a molecular weight in the range of 500-2500.

A modification of succinimide-polyamine compounds which is likewiseusable in accordance with the invention is described in U.S. Pat. No.6,569,819, which is hereby fully incorporated by reference. Furthersolvents suitable in accordance with the invention for dimericthiadiazoles are polyamine compounds containing terminal (R1/R2) phenylgroups or heterocyclic ring compounds, such as thiadiazoles orsuccinimide in combination with thiadiazoles. Compounds of this kind aredescribed, for example, in U.S. Pat. No. 5,597,785, which is herebyfully incorporated by reference.

The compounds of the formula (III) are used in accordance with theinvention, in alternative a), with a proportion by weight of 30% to 95%,preferably 40% to 60%, any desired mixtures of compounds of the formulae(III), (IV) and (V), preferably (IV) and (V), being possible.

Advantageously, the types of polyamine-based compounds mentioned are nota matter of ecological, toxicological or health concern.

Polyamines, and also the corresponding succinimide derivatives, have ahoney-like consistency at room temperature, become mobile when heatedabove 70° C. and are then capable of gradually dissolving dimeric2,5-dimercapto-1,3,4-thiadiazoles without residue. Alternative a) of theprocess of the invention is therefore preferably conducted at atemperature in the range from about 70° C. to about 140° C., morepreferably at a temperature in the range from about 80° C. to about 130°C., most preferably at a temperature in the range from about 80° C. toabout 120° C. At temperatures between 120° C. and 140° C.—highertemperatures may lead to decomposition reactions under somecircumstances—brown-red solutions are formed, but these are not usableany further after cooling because of a rubber-like consistency.

The dissolution capacity of the polyamine derivatives mentioned, theintense color of the solutions and the significant increase in viscosityindicate a marked interaction between dimeric thiadiazoles andpolyamines. It is apparent that adducts are formed, and these cannot bedistributed homogeneously in oily hydrophobic media at a relatively highactive ingredient concentration as required for attainment of thedesired EP properties, just like the corresponding dimeric thiadiazolesthemselves.

It has been found that, surprisingly, compounds of the formula (IV),namely linear compounds having a number of non-conjugated double bondsas occur, for example, in farnesene, lycopene or squalene, are suitablefor keeping these adducts in permanently liquid form even at roomtemperature. It can be assumed that steric mechanisms play a major rolein keeping the adducts separate in a spatially effective manner even athigh active ingredient concentrations. The use of compounds of theformula (IV) as a further medium in component step a) ii) is thereforean essential constituent of the present invention.

Among the compounds of the formula (IV), squalene (n=6) is particularlysuitable in accordance with the invention because of its favorableconsistency (viscosity) and its relatively low vapor pressure. Alsosuitable are molecules having relatively short chain lengths, but thelimiting factor for some applications is the significantly increasingvapor pressure or odor.

Higher chain lengths (n 9) lead to solids, which cannot be used inaccordance with the invention, at least at room temperature.

The compounds of the formula (IV) are used in accordance with theinvention in alternative a) with a proportion by weight of 10% to 60%,preferably 30% to 50%.

With squalene in conjunction with polyamine derivatives, it is thuspossible to prepare additive solutions having an active ingredientcontent of more than 10% by weight, the consistency of which remainswithin the manageable liquid range from 10° C. upward and which giveclear solutions in hydrophobic esters (vegetable oils or syntheticesters) as base oil in any ratio which is viable from the point of viewof the person skilled in the art.

In pure, entirely nonpolar oils such as paraffin or hydrophobicpolyglycol, however, this additive is unstable; the active ingredientgradually precipitates out. Therefore, it does not have unrestrictedusability in this form in practice.

The present invention therefore further provides the process accordingto alternative b).

Polyols usable with preference in component process step b) ii) are, forexample, hydrophobic polyether polyols of the formula (VII) having anethylene oxide/propylene oxide ratio<1

where m in the formula (VII) is an integer from 6 to 14, especially from6 to 10. Polyols usable with particular preference have an ethyleneoxide/propylene oxide ratio (EO/PO ratio) of <0.5.

Triglycerides with a hydroxy fatty acid component usable with preferencein component process step b) ii) are selected from those obtainable fromrenewable raw materials, especially from ricinoleic acid(12-(R)-hydroxy-9-cis-octadecenoic acid), lesquerolic acid(14-(R)-hydroxy-11-cis-eicosenoic acid),9-(S)-hydroxy-10,12-cis,cis-octadecadienoic acid (available from the oilof the seeds of Dimorphotheca pluvialis), phloionic acid(meso-9,10-dihydroxyocta-decanoic acid) and aleuritic acid.

Particular preference is given in accordance with the invention tocastor oil, which typically contains about 85% to 92% ricinoleic acid.

The compounds of the formula (I) or (II) are used in accordance with theinvention, in alternative b), with a proportion by weight of 3% to 6%,preferably 4% to 5%.

The polyols and/or triglycerides with a hydroxy fatty acid component areused in accordance with the invention, in alternative b), with aproportion by weight of 40% to 96%, preferably 50% to 80%.

Clear yellow solutions are formed within the temperature range fromabout 100° C. to about 140° C. Alternative b) of the process of theinvention is therefore preferably conducted at a temperature in therange from about 100° C. to about 140° C., more preferably at atemperature in the range from about 120° C. to about 140° C.

The saturation concentration for5,5′-dithiobis(1,3,5-thiadiazole-2-thiol) is about 4% to 5% by weight.After cooling, in the case of a high active ingredient concentration, ajelly-like mass can form, which can be dissolved very well, i.e. in abroad mixing ratio, even in hydrophobic polyglycol.

Very concentrated additive solutions have a gel-like consistencyespecially after standing for a prolonged period (about 1 month). Thecolor is clearly yellow. With castor oil, it is possible to produce amaximum of about 5% by weight solutions, which are of particularly goodsuitability for the additization of hydrophobic polyglycol types.

In contrast to the case of the lubricant additive obtainable accordingto a), it is also possible in the case of the additive obtainableaccording to b) to add relevant amounts of additive in paraffin-basedmedia without precipitation. The nonpolar media here should preferablycontain at least 10% by volume of polyglycol or castor oil in order toattain the requisite stability.

Hydrophobic phenol derivatives usable with preference in componentprocess step b) iii) are selected from anacardic acid, cardol, cardanol.

Unsaturated fatty alcohols usable with preference in component processstep b) iii) are selected from hexadecenol, octadecenol.

The hydrophobic phenol derivatives and/or unsaturated fatty alcohols areused in accordance with the invention, in alternative b), with aproportion by weight of 40% to 96%, preferably 50% to 80%.

By precipitation reactions, it was possible to detect, both in the caseof the additives obtainable according to a) and in the case of thoseobtainable according to b), that no chemical conversions took place withregard to the starting materials.

It is also possible to produce stable sols extending as far as stablemicrofine dispersions from both systems with appropriate dispersingadditions, especially with additional polyamines and derivativesthereof.

The following examples illustrate the invention, but without restrictingit thereto:

EXAMPLES Example 1

A dimeric thiadiazole having a proportion by weight of 4% is distributedhomogeneously into a mixture having a proportion by weight of up to 50%rapeseed oil and a further proportion by weight of up to 50%dialkyl-succinimide dispersant with stirring at a maximum of 140°, inthe course of which a dark red liquid gradually forms. Further additionssuch as benzotriazole (as preservative, not as nonferrous metaldeactivator) are added with a proportion by weight of up to 0.5%. Aftercooling, a stable viscous liquid is obtained, into which is mixed a baseoil based on rapeseed oil up to a proportion by weight of 5%.

For comparison with zinc alkyldithiophosphate, an experiment wasconducted with a four-ball apparatus. The base oil used for all theadditives mentioned was Flexon 845 ISO VG 32 hydraulic base oil(available from Esso). It was found that the thiadiazole (dimer)additive gave the best values at comparable concentrations. In the caseof zinc alkylphosphate, the good load and welding load values werebetween 1600 N and 1700 N, and in the case of thiadiazole (dimer)between 2100 N and 2300 N.

Example 2

A flask is charged with a proportion of 60% squalene, 30%polyisobutylenesuccinimide (CAS no. 84605-20-9) and about 10% dimeric2,5-dimercapto-1,3,4-thiadiazole (CAS no. 72676-55-2), and heated toabout 135° C. The thiadiazole is dissolved completely to form ared-brown liquid. As a further addition, preservatives are addedthereto. Cooling leaves a readily manageable viscous liquid, which canbe used as EP additive.

This additive was added to the Flexon 845 ISO VG 32 hydraulic oil(available from Esso) in different concentrations, and the samples weresubjected to a four-ball test. The results are recorded in the followingtable:

Additive concentration 1.00% 2.50% 5.0% in Flexon 845 ISO VG 32Appearance clear clear clear solution solution solution Four-ball test(ASTM D 4172) 1 h, 75° C., 400 N, 1200 rpm Wear diameter (mm) 0.50 0.680.69 Four-ball test (ASTM D 2783) 10 s, 25° C., 1800 rpm Good load in N1800 2200 3000 Welding load in N 2000 2400 3200

Example 3

96% castor oil and 4% by weight of dimeric2,5-dimercapto-1,3,4-thiadiazole (CAS no.: 72676-55-2) are heated to140° C. in a flask, in the course of which the thiadiazole dissolvesgradually. This forms a yellow transparent liquid, to which preservativeis added while it is in the hot state. After cooling, the mixture can beused as additive to polyglycol-based (hydrophobic) lubricants, or elseas anticorrosive for nonferrous metals.

Copper corrosion was measured with different additization of EmkaroxVG126 polyglycol (from Croda).

The results of the corrosion measurement are as follows:

Emkarox VG126 with 2.5% 5.0% 7.0% additive additive additive additiveCopper corrosion (ASTM D 130) 100° C., 24 hours 1b 1b 1b

Example 4

Example of the preparation of a thiadiazole solution with the aid ofphosphoric esters:

200 mL of tributoxyalkyl phosphate (AW11 Schafer Chemie) and 270 mL ofparaffin (of low viscosity) are heated to 90° C. in a round-bottomflask. 40 g of dimeric thiadiazole are added in several portions until aclear solution forms. In order to assure storage life (bacterialinfestation), a small amount (in the permille range) of benzotriazolewhich has been dissolved in a small amount of tributoxyalkyl phosphatebeforehand is stirred into the still-hot solution. After cooling, thesolution is usable.

It dissolves in any ratio in paraffin or else in mineral oil.

The invention further provides a lubricant additive obtainable by theprocess of the invention.

The invention further provides a lubricant additive comprising

-   I. a dimeric thiadiazole compound, especially a    bis(2-alkyl-1,3,4-thiadiazolyl) 5,5′-disulfide derivative of the    formula (I)

-   -   and/or a dimeric 2,5-dimercapto-1,3,4-thiadiazolethiol        derivative of the formula (II)

-   -   where n in the formulae (I) and (II) is 1 or 2 and R1 and R2 are        each independently hydrogen, linear or branched alkyl groups        having 1 to 12 carbon atoms, especially thioalkyl groups (—SR)        having 1 to 12 carbon atoms, aromatic radicals or heteroaromatic        radicals,

-   II. a polyamine or polyamine derivative of the formula (III)

R1-(CH2-CH2-NH)n-CH2-CH2-R2  (III)

-   -   where n in formula (III) is an integer from 1 to 15, especially        an integer from 3 to 8, and    -   R1 and R2 are each independently hydrogen, —NH2, linear or        branched alkyl groups having 1 to 12 carbon atoms or a modified        or unmodified succinimide group, and

-   III. a compound of the formula (IV)

-   -   in which n is an integer from 1 to 8, especially an integer from        3 to 8, preferably 6.

The invention further provides a lubricant additive comprising

-   I. a dimeric thiadiazole compound, especially a    bis(2-alkyl-1,3,4-thiadiazolyl) 5,5′-disulfide derivative of the    formula (I)

-   -   and/or a dimeric 2,5-dimercapto-1,3,4-thiadiazolethiol        derivative of the formula (II)

-   -   where n in the formulae (I) and (II) is 1 or 2 and R1 and R2 are        each independently hydrogen, linear or branched alkyl groups        having 1 to 12 carbon atoms, especially thioalkyl groups (—SR)        having 1 to 12 carbon atoms, aromatic radicals or heteroaromatic        radicals,

-   II. a polyol, especially a polyether polyol having a high propylene    oxide content, i.e. having a low ethyl oxide/propylene oxide ratio,    and/or a triglyceride having a hydroxy fatty acid component, and

-   III. a hydrophobic phenol derivative and/or unsaturated fatty    alcohol.

The proportions by weight of the constituents of the additives of theinvention correspond to those specified for the production process.

The invention further provides a lubricant, especially a lubricant oil,comprising an additive of the invention, preferably in a concentrationof 0.2% by weight to 10% by weight.

The invention further provides for the use of an additive of theinvention in lubricants, especially for slide bearings, roller bearings,gears, chains, fine mechanics, slideways, motors, hydraulics, tools,machines, metalworking operations, material-removing metalworking andcold forming. Accordingly, lubricants of the invention are distinguishedby the field of use, for example as machine lubricant oils, cylinderoils, turbine oils, motor oils, transmission oils, compressor oils,circulation oils, hydraulic oils, insulation oils, carrier oils, processoils, metalworking oils, cooling lubricants, cutting oils and lubricantgreases. Preference is given in accordance with the invention to use inlubricant oils, especially in mineral oil-free forming lubricants.

Preference is likewise given in accordance with the invention to the useof an additive of the invention in lubricants which are used in the foodsector, in medical technology, or else for lubrication in the “open seaoffshore sector” (open sea wind turbines).

The lubricants of the invention, especially lubricant oils, generallyconsist of a base oil and the additives of the invention and possiblefurther additives.

Base oils used may especially be mineral oils, for example mineral oildistillate fractions; synthetic oils, for example polyethers such aspolyglycols and polyphenyl ethers; carboxylic esters; phosphoric andphosphonic esters; silicones; silicate esters and polyolefins ormixtures thereof.

Phosphoric esters preferred in accordance with the invention are thosewhich contain, apart from the strongly polar phosphate group, also atleast one or better more than one polar group (ethoxy, butoxy groups)and simultaneously have long C—C chains (C8 to C14). Particularpreference is given to tributoxyalkyl phosphate having chain lengths ofC9 to C12. Preference is likewise given to alkoxy-substituted triphenylphosphates and trialkylammonium phosphites. The alkyl chain lengths onthe nitrogen here are preferably 9 to 14. Also usable in accordance withthe invention are dialkyl phosphates having chain lengths of 8 to 12,and likewise alkoxylated dialkyl phosphates. Thiadiazole solutionscomprising tributoxyalkyl phosphate can be introduced into almost allmedia (especially mineral oil-based media) without any great miscibilitygaps. Phosphoric esters likewise preferred in accordance with theinvention are phosphoric esters with oleyl ethoxylate radicals as shownin formula IX in which R is hydrogen or

Further usable additives are, for example, oxidation inhibitors, forexample sterically hindered phenols, amines, zinc dithiophosphates;corrosion and rust inhibitors, for example amine phosphates,alkylsuccinic acids, fatty acids; friction modifiers, for example fattyacids, fatty amines; detergents, for example standard or basic Ca, Baand Mg sulfonates or Ca, Ba and Mg phosphonates; dispersants, forexample polymers such as nitrogen-containing polymethacrylates,alkylsuccinimides, succinate esters; pour point depressants, for examplealkylated naphthalenes and phenols; viscosity index improvers, forexample polyisobutylenes, polyacrylates, hydrogenated styrene-butadienecopolymers; foam inhibitors, for example silicone polymers, tributylphosphate; adhesion improvers, for example soaps, polyacrylates;emulsifiers, for example sodium salts of organic sulfonic acids, fattyamine salts; bactericides, for example phenols or formaldehydederivatives.

1. A process for producing a lubricant additive, wherein a) i) a dimericthiadiazole compound, especially a bis(2-alkyl-1,3,4-thiadiazolyl)5,5′-disulfide derivative of the formula (I)

and/or a dimeric 2,5-dimercapto-1,3,4-thiadiazolethiol derivative of theformula (II)

where n in the formulae (I) and (II) is 1 or 2 and R1 and R2 are eachindependently hydrogen, linear or branched alkyl groups having 1 to 12carbon atoms, especially thioalkyl groups having 1 to 12 carbon atoms,aromatic radicals or heteroaromatic radicals, ii) is dissolved in apolyamine or polyamine derivative of the formula (III)R1-(CH2-CH2-NH)n-CH2-CH2-R2  (III) where n in formula (III) is aninteger from 1 to 15, especially an integer from 3 to 8, and R1 and R2are each independently hydrogen, —NH2, linear or branched alkyl groupshaving 1 to 12 carbon atoms or a modified or unmodified succinimidegroup, and iii) a compound of the formula (IV)

in which n is an integer from 1 to 8, especially an integer from 3 to 8,preferably 6, is added to the solution obtained, or b) i) a dimericthiadiazole compound, especially a bis(2-alkyl-1,3,4-thiadiazolyl)5,5′-disulfide derivative of the formula (I)

and/or a dimeric 2,5-dimercapto-1,3,4-thiadiazolethiol derivative of theformula (II)

where n in the formulae (I) and (II) is 1 or 2 and R1 and R2 are eachindependently hydrogen, linear or branched alkyl groups having 1 to 12carbon atoms, especially thioalkyl groups (—SR) having 1 to 12 carbonatoms, aromatic radicals or heteroaromatic radicals, ii) is dissolved ina polyol, especially a polyether polyol having a high propylene oxidecontent and/or a triglyceride having a hydroxy fatty acid component, andiii) a hydrophobic phenol derivative and/or unsaturated fatty alcohol isadded to the solution obtained.
 2. The process as claimed in claim 1,wherein in alternative a), the dimeric thiadiazole compound used is5,5′-dithiobis(1,3,5-thiadiazole-2-thiol), and/or in alternative a), thepolyamine or polyamine derivative of the formula (III) used is themono-succinimide derivative of the formula (V) or the bissuccinimidederivative of the formula (VI), and/or in alternative a), the compoundof the formula (IV) used is farnesene, lycopene or squalene.
 3. Theprocess as claimed in claim 1, wherein in alternative b), the dimericthiadiazole compound used is 5,5′-dithiobis(1,3,5-thiadiazole-2-thiol),and/or in alternative b), the polyol used is a hydrophobic polyetherpolyol of the formula (VII), and/or in alternative b), the triglyceridehaving a hydroxy fatty acid component used is castor oil or ricinoleicacid, and/or in alternative b), the hydrophobic phenol derivative usedis cardol, cardanol or anacardic acid, and/or in alternative b), theunsaturated fatty alcohol used is hexadecenol or octadecenol.
 4. Theprocess as claimed in claim 1, wherein the compounds of the formulae (I)and (II) in alternative a) are used with a proportion by weight of 4% to13%, preferably 8% to 10%, and the compounds of the formula (III) inalternative a) are used with a proportion by weight of 30% to 95%,preferably 40% to 60%, and the compounds of the formula (IV) inalternative a) are used with a proportion by weight of 10% to 60%,preferably 30% to 50%, or the compounds of the formulae (I) or (II) inalternative b) are used with a proportion by weight of 3% to 6%,preferably 4% to 5%, and the polyols and/or triglycerides with a hydroxyfatty acid component in alternative b) are used with a proportion byweight of 40% to 96%, preferably 50% to 80%, and the hydrophobic phenolderivatives and/or unsaturated fatty alcohols in alternative b) are usedwith a proportion by weight of 40% to 96%, preferably 50% to 80%.
 5. Thelubricant additive obtainable according to claim
 1. 6. A lubricantadditive comprising I. a dimeric thiadiazole compound, especially abis(2-alkyl-1,3,4-thiadiazolyl) 5,5′-disulfide derivative of the formula(I)

and/or a dimeric 2,5-dimercapto-1,3,4-thiadiazolethiol derivative of theformula (II)

where n in the formulae (I) and (II) is 1 or 2 and R1 and R2 are eachindependently hydrogen, linear or branched alkyl groups having 1 to 12carbon atoms, especially thioalkyl groups having 1 to 12 carbon atoms,aromatic radicals or heteroaromatic radicals, II. a polyamine orpolyamine derivative of the formula (III)R1-(CH2-CH2-NH)n-CH2-CH2-R2  (III) where n in formula (III) is aninteger from 1 to 15, especially an integer from 3 to 8, and R1 and R2are each independently hydrogen, —NH2, linear or branched alkyl groupshaving 1 to 12 carbon atoms or a modified or unmodified succinimidegroup, and III. a compound of the formula (IV)

in which n is an integer from 1 to 8, especially an integer from 3 to 8,preferably
 6. 7. A lubricant additive comprising I. a dimericthiadiazole compound, especially a bis(2-alkyl-1,3,4-thiadiazolyl)5,5′-disulfide derivative of the formula (I)

and/or a dimeric 2,5-dimercapto-1,3,4-thiadiazolethiol derivative of theformula (II)

where n in the formulae (I) and (II) is 1 or 2 and R1 and R2 are eachindependently hydrogen, linear or branched alkyl groups having 1 to 12carbon atoms, especially thioalkyl groups having 1 to 12 carbon atoms,aromatic radicals or heteroaromatic radicals, II. a polyol, especially apolyether polyol having a high propylene oxide content, i.e. having alow ethyl oxide/propylene oxide ratio, and/or a triglyceride having ahydroxy fatty acid component, and III. a hydrophobic phenol derivativeand/or unsaturated fatty alcohol.
 8. The lubricant, especially lubricantoil, comprising a lubricant additive as claimed in claim 5, preferablyin a concentration of 0.2% by weight to 10% by weight.
 9. The use of alubricant additive wherein in claim 5 in lubricants and especiallylubricant oils, more preferably in mineral oil-free forming lubricants.